Supporter groups are made up of rabid fans. From what I understand, Çarşı is no longer operational, so I don't know if it qualifies as the best. 'The Cove' is an Australian supporter group that still exists, and you can find many more in Australian football.

Being a graduate of the University of Florida, I would say that Gator fans are the best support group for college football in America. There are Gator Clubs in most large American cities, and the Orange and Blue often dwarfs home team colors at away games.